272 ELIZABETH A. SMITH. 



dermic syringe with a small needle was used. The dorsal part 

 of the abdomen was then cut off and the nymph placed in a 

 dissecting pan of water. The testes were removed as quickly 

 as possible to a vial containing the fixing fluid used for injection. 

 Where Bouin's fluid was used for killing, the dissection was 

 made in 70 per cent, alcohol instead of water. The best results 

 for working out the different stages, especially those of the 

 growth period, were derived from fixation in Bouin's fluid fol- 

 lowed by Heidenheim's iron-haematoxylin w T ith eosin or acid 

 fuchsin as counter stains. Some excellent preparations were 

 obtained by staining with an aqueous solution of safranin for 

 two minutes, followed by lichtgriin. Good results also followed 

 the use of a saturated aqueous solution of Gentian violet and 

 orange G after fixation with Flemming's solution. 



For quick observations upon fresh material aceto-carmine 

 was used. Cells stained with this swell slightly but cytological 

 details such as chromosomes, spindle, centrosome and spireme 

 are brought out clearly. Satisfactory counts of polar views and 

 camera-lucida drawings could easily be made. The details 

 obtained in these entire cells could be used as a check in ex- 

 amining sections. 



Testes were also teased and mounted unstained upon a slide 

 in Ringer's and in physiological salt solutions. Normal saline 

 caused plasmolysis after a short interval, but tissue placed in 

 Ringer's solution made up with a .5 per cent, normal salt instead 

 of .7 per cent, remained normal for several hours before signs of 

 disintegration began. The chromosomes in both Sympetrum 

 and Libellula could be seen in the fresh material, as they have a 

 refractive power which differs from that of the cytoplasm. The 

 chromosomes upon the spindles both in the metaphase and 

 anaphase could be distinguished as separate bodies in the pri- 

 mary spermatocyte division. In growth stages a spireme was 

 visible while in the spermatogonia the chromatin nucleolus was 

 evident. This proves that the details of the cell, as revealed in 

 preserved materials, are reasonably faithful presentations of the 

 conditions which really prevail in the living cell. Complete cell 

 division was not observed. Cells teased apart remain connected 

 by long protoplasmic threads. The fact that the chromosomes 



